Color television tube



y 1957 A. B. WELCH 2,792,522

COLOR TELEVISION TUBE Filed Sept. 18, 1953 Phase Phase Phase 25 I7 shif;snug Shift l 1 Tuned Amplifier 44 i 3 2 G 2e 36 Electron Beam 1 5 Y 52was L. 42 a .4.

- Fig.3. g

\ INVENTOR Albert B. Welch.

t B G R G R B G R B V ATTORNEY COLOR TELEVISEON TUBE Albert B. Welch,Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application September 18,1953, Serial No. 381,067

12 Claims. (Cl. 315-12) This invention relates to cathode ray tubes andmore particularly to improvements therein for obtaining control signalscorresponding to the position of the electron beam.

It is an object of my invention to provide an improved cathode ray tubefor the reproduction of a television image in natural colors.

t is another object to provide an improved system for the reproductionof color images in which a video signal representative of a given coloris applied at a predeterl ined point on the scanning raster of thecathode ray tube to modulate the intensity of the electron beam.

it is another object to provide an improved system for the reproductionof color images in which a video signal representative of a given coloris applied at a predetermined time on the scanning raster of the cathoderay tube to modulate the intensity of the electron beam.

it is another object to provide an improved sensing system to obtaincontrol signals corresponding to the position of the electron beam onthe scanning raster of a cathode ray tube.

These and other objects are effected by my invention as will be apparentfrom the following description taken in accordance with the accompanyingdrawing throughout which like reference characters indicate like parts,and in which:

Figure 1 is a representation of a television receiving system embodyingmy invention;

Fig. 2 is a partial perspective view of a screen which may beincorporated into the cathode ray tube shown in Fig. 1;

Fig. 3 is a front view illustrating a modification of a portion of thescreen shown in Fig. 2 embodying my invention which may be incorporatedinto the cathode ray tube shown in Fig. 1; and

Fig. 4 shows a sectional top view of a modified target structure whichmay be utilized in the cathode ray tube shown in Fig. 1 embodying myinvention.

Referring in detail to Fig. 1, a special cathode ray tube is providedcomprising an evacuated envelope 12 of suitable shape and material. Anelectron gun 14 of a suitable type is provided in the neck portion 16 ofthe envelope 12. A cathode 13, an intensity control element 2% and afocusing electrode 22 of the electron gun 14 are shown for purposes ofexplanation. An electron beam 13 projected by the electron gun 14 isprovided with a suitable electrostatic or electromagnetic deflectionmeans for scanning a raster I have illustrated electromagneticdeflection means schematically by the deflection coils 24.

The electron beam 13 is projected toward the viewing face 26 of theenvelope 12. A target assembly 28 is provided within the envelope forthe electron beam 13, and is positioned near the viewing face 26.

A shielding electrode 3% which is of a transparent conductive materialis deposited on the interior or exterior surface of the face plate 26and serves tov reduce any stray electrostatic pickup by the targetassembly 28. The target assembly 23 comprises a collecting electrode 32positioned 2,792,522 Patented May 14, 1957 ear the viewing face 26. Thecollecting electrode 32 is of a transparent conductive material such asNesa. The collecting electrode 32 may be supported in any known manner.An output terminal 38 is provided for the collecting electrode 32through the envelope 12 to the exterior thereof. A screen member 40 anda part of the target structure 28 is positioned between the electron gun14 and the collecting electrode 32. The screen 40 comprises a supportingmember 42 of a transparent mate rial having a phosphor coating 44applied on the side thereof facing the electron source 14.

The phosphor coating 44 comprises a plurality of groups of phosphorstrips or lines B, G, R. In the em bodiment shown of a three-colorsystem, each group contains in the following sequence a first strip B ofa phosphor material such as zirconium silicate activated by silver thatemits blue light upon electron bombardment, a second strip G of aphosphor material such as zinc cadmium sulphide activated by silver thatemits green light upon electron bombardment, and a third strip R of aphosphor material such as aluminum borilicate activated by chromium thatemits red light upon electron bombardment.

In the embodiment shown in Fig. 1, the phosphor lines B, G and R arevertical with respect to the viewer with the electron beam 13 scanning araster transverse to the phosphor lines B, G and R. However, it may bedesirable in some applications that the phosphor lines B, G and R behorizontal or at an angle with the horizontal. The orientation of thephosphor lines is limited only in that the electron beam 13 must scanacross the phosphor lines B, G and R.

The phosphor lines B, G and R may be depositedon the support member 42in any suitable manner such as silk screening. The phosphor lines B, Gand R may be deposited so that each group substantially covers theentire surface of the support member 42 as shown in Fig. 2 or may bemade narrow to cover only a part of the entire area of the supportmember 42 as shown in Fig. 3. The advantage of utilizing a narrow stripphosphor line with an uncovered area between each of the phosphor stripsG, B and R is that the electron beam 13 may have a larger diameterwithout causing color contamination.

In Fig. 2 I have shown an embodiment of the screen structure 40 shown inFig. 1. The screen structure 40 contains a plurality of strip areas 50on the surface of the support member 42, upon which no phosphor has beendeposited. This strip area 50 precedes each group of phosphor strips B,G and R. The strip 50 has substantially the same width as any of thephosphor strips G, B and R. Within the exposed strip area 50 there areprovided electron apertures or electron transmissive regions 52 in thesupport member 42. One possible method of placing the apertures 52 inthe supporting member 42 would be the utilization of a glass material asthe supporting member 42 and photoetching of the desired apertures 52prior to the depositing of the phosphor strips G, B and R. The apertures52 may be of any suitable length or size and the separation between theapertures 52 on the strip area 50 should be of less distance than thediameter of the electron beam 13. The construction as shown in Fig. 2 ofusing a plurality of apertures 52 rather than one elongated aperturecovering current voltage source 11 of the order of lgilovolts isconnected to the shell 54 and the screen 40. The high voltage source 11is also connected through a resistor 15 to the terminal 38 of thecollecting electrode 28. The terminal 38 of the collecting electrode 23is also connected through a condenser 17 to a tuned limiting band passamplifier 19. The tuned circuit of the amplifier 19 is designed toresonate at a frequency corre sponding to the rate of color groupscanning and the tuned circuit is driven by the pulse component receivedfrom the collecting electrode 28. The tuned circuit of the amplifier 19may also be adjusted to the most prominent frequency componentcorresponding to the aperture scanning rate and the frequency multipliedto the color group scanning rate. The output of the amplifier .19 isconnected to three separate phase shift circuits 21, 23 and 25. Thephase shift circuits 21, 23. and 25 are connected respectively to agreen, blue and red video gate. The video signals representative ofgreen, blue and red video information are connected through theirrespective gating circuits to a common connector 27 which is connectedto the intensity control electrode of the electron gun 14.

The operation of the apparatus of Figs. 1. and 2 may be described asfollows. The electron gun 14 projects an electron beam 13 toward thetarget structure 28. The electron gun 14 is biased so that a smallcurrent will flow without video information applied to the intensitycontrol electrode 20 of the electron gun 14. This small current or darkcurrent must be of sufiicient value that when the electron beam 13passes through one of the apertures 52, a signal will be obtained fromthe collecting electrode 32 of sufiicient value to actuate the controlcircuit to gate the video channels.

A deflection signal derived from a suitable receiving circuit (notshown) is applied to the deflection coils 24 to cause the electron beam13 to scan a raster on the screen 40 transversely to the phosphor stripsG, B and R.

As the electron beam 13 scans across the screen 40, a pulse is generatedin the collecting electrode 32 each time the electron beam 13 scansacross an aperture 52. The alternating component of pulsating directcurrent obtained from the collector 32 passes through the blockingcondenser 17 to the tuned amplifier circuit 12. The tuned circuitamplifier 9 is adjusted to resonance at a frequency correspondirv to therate of color group scanning, and the pulses impressed thereon drive theresonant circuits of the amplifier 19. The output of the amplifier 19 isconnected to three phase shiftcircuits 21,23, of suitable type whichdelays the sine wave received from the amplifier in such a manner thatthe phase shift circuit 25 will open the red gate permitting red videoinformation to be applied to the intensity control electrode 20 of theelectron source 14 when the scanning beam 13 is approximately in thecenter of the R phosphor strip. The phase shift circuit 21 whichcontrols the gating circuit in the green video information channel opensthe green video channel permitting video information to be applied tothe intensity control grid 20 of the electron source 14 substantiallywhen the electron beam 13 is in the center of the G phosphor strip. Thephase shift circuit 23 which controls the gating circuit within the bluevideo information channel opens the blue gate when the electron beam 13is substantially on the center of the B strip. By utilizing a sine waveto control the gating circuits, it is possible to have the videoinformation applied to the phosphor strips G, B and R reach a maximumsubstantially at the center of each strip which will decrease thepossible color contamination.

In Fig. 3 I have shown another modification of the screen shown in Fig.2. This modification has several advantages over the slit type screenutilized in Pig. 2. The use of round or square holes presentsa, lessnoticeable aperture pattern than a series of slits to the obr: S u re.hol s perm more Posit on. sens n cur; rent to pass through than roundholes when the beam is scanning a path halfway between the horizontalcenter lines of apertures while it is possible that fabrication of theround holes would be less difficult. The use of the round or squareapertures 52 shown in Fig. 3 spaced horizontally at some multiple of thecolor group repetition rate permits placing phosphor strips of one colordirectly on the vertical center lines of the apertures. The overallbrightness of the image will not be lost if the apertures 52 are placedin the most eificient of the color phosphors such as blue or green. Themodification shown in Fig. 3 allows greater center-to-center spacing ofthe color strips G, B and R and permits the use of larger electron beamdiameters without color contamination. The device in Fig. 3 also has theadvantage that the strips G, B and R may be made narrow to cover onlypart of the total area of the screen. The incorporation of the screen ofFig. 3 into Fig. 1 would not change the operation of the tube.

In my invention it is required that a small spot or sharply focusedelectron beam 13 be used to prevent color contamination. As the electronbeam scans up and down or from left to right from the center of thescreen surface 49, the required focal length for the electron beam 13varies. The focal length of the electron lens may be varied in knownmanners, such as dynamic focusing techniques, or by curving the screento the shape of a spherical section with a center of radius at thecenter of deflection of the electron beam. By curving the screen theelectron beam focal length is constant over the entire screen.

In Fig. 4 I have shown a modified target assembly structure 28 in whichthe screen 40 comprising the supporting member 42 and the phosphorcoating 44 deposited thereon are of similar nature to that shown inFigs. 1 and 2 but on the rear side of the supporting structure 42 withrespect to said electron gun 14 is deposited an electron sensitive layer56 of a transparent conductive layer. The receptor or collectorelectrode 32 of Fig. l is modified by depositing a transparent coating36 on the side of a supporting structure 34 of a material capable ofhigh secondary emission to form an electrode 58. In this application thesensing signal would be obtained from the electron sensitive layer 56rather than the electrode 58.

The operation of the modified targetassembly 28 shown in Fig. 4 would besimilar to that described above as to Figs. 1 and 2, except that theelectrons in the electron beam 13, after passing through apertures 52,would strike the secondary emissive layer 36 of the electrode 58, andthe secondary and reflected primary electrons would be collected by theelectron sensitive layer 56 to obtain a sensing signal. This wouldresult in an amplification of the sensing signal by the secondaryemission of the layer 36. The device shown in Fig. 4 also requires thatthe voltage on the electron sensitive surface 56 be of a positive valuecompared to that on the electrode 58 to collect the electrons.

My invention provides a device which is simple in construction, does notsuffer from ambient light and various other problems associated withthose devices utilizing photocell sensing pickup. My device also doesnot have the high capacitance between the final anode and conductingstrips on the screen, nor does it suffer from the masking effect of asensing grid positioned between the screen and the electron source. Myinvention also permits the use of a minimum number of apertures acrossthe screen, and also the tuned amplifiers provide a sine wave whichpermits the use of a simple resistor-capacitor combination in lieu ofthe delay line network commonly associated with this type of electronbeam control.

While I have shown my invention in several forms,

it: will be obvious to those skilled in the art that it is not solimited but is susceptible of various other changes and modificationswithout departing from the spirit and scope thereof.

I claim as my invention:

1. A television tube comprising an evacuated envelope, an electronsource for projecting an electron beam, a target electrode for saidelectron beam, said target electrode comprising a support member havinga plurality of phosphor area deposited on the surface thereof facingsaid electron source, said target electrode having a plurality ofapertures, a receptor electrode positioned on the opposite side of saidtarget electrode with respect to said electron source for interceptingelectrons passing through the apertures of said target electrode forproducing a control signal in response to the bombardment of saidelectrons and means for utilizing said control signal to control theexcitation of said phosphor areas by said electron beam.

2. A color television tube comprising an evacuated envelope, means forprojecting an electron beam, a target for said electron beam having aplurality of vertical phosphor strips, said target also having aplurality of apertures uniformly spaced transversely across saidphosphor strips, a secondary electron emissive surface positioned to therear of said target for intercepting electrons passing through theapertures of said target, and mean for collecting the secondary emissionfrom said electron emissive surface.

3. A color television tube comprising an image screen, said screencomprised of a support member having a plurality of adjacent groups ofvertical phosphor strips thereon, each of said groups of phosphor stripsrepresentative of the selective component colors and each strip withineach of said groups representative of a different selected colorcomponent, said image screen having a plurality of vertical rows ofapertures, said rows of apertures being spaced uniformly horizontallyacross said image screen, an electron beam scanning mean for scanning araster on said image screen transversely to said phosphor strips, andoutput means for deriving a signal in response to the electrons passingthrough said apertures.

4. A color television tube comprising an image screen, said image screencomprising a support member having a plurality of adjacent groups ofvertical phosphor strips thereon, each of said groups of phosphor stripsbeing representative of the selective component colors and each stripwithin each of said groups being representative of a difierent selectedcolor component, said image screen having electron transmission sectionsuniformly spaced Within selected phosphor strips, means for scanning anelectron beam raster transversely to said phosphor strips,

and a receptor electrode positioned to the rear of said image screenwith respect to said scanning mean for intercepting electrons passingthrough said transmission sections.

5. A color television tube comprising an image screen having a pluralityof adjacent groups of vertical phosphor strips, each of said groups ofphosphor strips being representative of the selective component colorsand each strip Within each of said groups representative of a differentselected color component, said image screen having a plurality ofvertical rows of apertures in registration with each of a selectedcomponent color phosphor strip, an electron gun with means for scanninga raster transversely to said phosphor strips, and means positioned tothe rear of said image screen with respect to said electron gun forderiving the electron current passing through the apertures in saidimage screen.

6. A color television tube comprising an image screen having a pluralityof adjacent groups of vertical phosphor strips, each of said groups ofphosphor strips being representative of the selective component colorsand each strip within each of said groups representative of a difl'erentselected color component, said image screen having electron transmissionsections positioned within a selected color phosphor strip or eachgroup, an electron source 6 with means for scanning said phosphor stripstransversely and a receptor electrode positioned to the rear of saidimage screen so as to intercept electrons passing through said electrontransmission sections.

7. A color television tube comprising an image screen having a pluralityof adjacent groups of vertical phosphor strips, each of said groupshaving a first phosphor capable of emission of light of a blue color, asecond phosphor strip capable of emission of light of a green color, athird phosphor strip capable of emission of light of a red color, saidimage screen having a plurality of apertures located in each of saidfirst phosphor strips, means for scanning said phoshor stripstransversely with an electron beam, and an electron sensitive electrodepositioned to the rear of said image screen with respect to saidelectron beam.

8. A color television tube comprising an image screen having a pluralityof adjacent groups of vertical phosphor strips, each of said groupshaving a first phosphor capable of emission of a blue color light, asecond phosphor strip capable of emission of a green color light, athird phosphor strip capable of emission of a red color light, electrontransmission sections located in each of said phosphor strips capable ofemission of light of a blue color, means for scanning said phosphorstrips transversely with an electron beam and an electron sensitiveelectrode positioned on the opposite side of said image screen withrespect to said electron beam for producing a control signal.

9. A color television image reproducing system comprising thecombination of an image screen having a plurality of groups of verticalphosphor strips, each of said groups of phosphor strips beingrepresentative of the selected component colors and each strip withinsaid group representative of a diiferent selected component color, saidimage screen having a plurality of rows of apertures uniformly spacedhorizontally across said image screen, an electron gun for scanning saidphosphor strips transversely with an electron beam, a secondary emissiveelectrode positioned on opposite side of said image screen with respectto said electron gun and an electron sensitive layer for developing asensing signal.

10. A color television tube comprising an image screen, said imagescreen comprising a foundation of a transparent material having aplurality of groups of adjacent vertical strips of phosphor materialdeposited thereon, each of said groups of phosphor strips beingrepresentative of selected component colors and separated by an uncoatedarea, said uncoated area having a plurality of apertures locatedtherein, an electron gun for scanning a raster on said image screen anda transparent electron sensitive electrode positioned on the oppositeside of said image screen with respect to said electron gun forproducing a control signal, and means for utilizing said control signalto gate said electron gun.

11. A color television tube comprising an image screen, said imagescreen comprising a supporting number of transparent materials having aplurality of vertical phosphor strips, a first strip comprising acoating of phosphor material capable of emission of light of a bluecolor, a second strip comprising a phosphor material capable of emissionof light of a green color and a third strip comprising a phosphormaterial capable of emission of light of a red color, each of saidphosphor strips being separated by an uncoated area, uniformly spacedapertures located in each of said first strips, an electron gun forscanning a raster transversely to said phosphor strips, output means forproducing a control signal in response to the passage of electrons fromsaid electron beam through the apertures in said image screen, and meansfor utilizing saidcontrol signal to control the excitation of saidphosphor strips for said electron gun.

12. In combination a scanning system comprising an apertured targetelectrode to be scanned, said target electrode comprising a supportmember and a plurality of electron sensitive areas thereon, an electrongun for producing an electron beam, said electron beam having movementrelative to said target for scanning said target, an

electron sensitive electrode output means separated from V andpositioned on the opposite side of said target electrode with respect tosaid electron gun for producing a control signal in response toelectrons passing through said apertures, and means for utilizing saidcontrol signals to gate said electron beam.

References Cited in the file of this patent UNITED STATES PATENTS VanGelder et a1. Dec. 5, 1950 Rose n Dec. 4, 1951

